Muffler for pneumatic motor

ABSTRACT

A hydraulic pump and double acting air motor therefor including means for controlling the inlet and exhaust of air to and from the opposite sides of the piston in the air cylinder. A pilot valve operated by the air piston controls one operating valve for the cylinder and a pilot relay valve. The pilot relay valve controls another operating valve which is in reverse phase with respect to the first operating valve. A muffler which inhibits ice formation is operatively associated with the operating valves for muffling the noise of the air being exhausted from the air cylinder through the operating valves with minimal accumulation of ice.

United States Patent Rosen et al.

1451 July 11,1972

s4] MUFFLER FOR PNEUMATIC MOTOR 3,339,668 9/1967 Trainor 181/36 A 121IIIVCIIIOISI s 1 a. Rosen, Lorain; 111m A. m, if}??? m' i ay;

woman "Lil I ma of Ohio FOREIGN PATENTS on APPLICATIONS 1 1 s NM mmAmherst. Ohio 932,373 7/1963 Great Britain .......................181/36A [22] Filed: my 1971 Primary Examiner-Robert S. Ward, Jr. [21]Appl.No.: 144,124 AuorneyBosworth,Seaaions,1-lerratrom&Cain

Related US. Applesfion Data [57] ABSTRACT [62] Division of Ser. No.809,235, March 21, 1969. A hydraulic pump and double acting air motortherefor including means for controlling the inlet and exhaust of air to[52) US. Cl. ..l8l/36 A, 181/40, 181/65, and from the opposite sides ofthe piston in the air cylinder. A 181/47 A, 181/57 pilot valve operatedby the air piston controls one operating 51] 161. c1. "F01! 1/011, F01111/22 valve for the cylinder and a pilot relay valve The pilot relay [58]Fleltlflsfll'tll ..181/35 R, 36 R, 36A, 40, 47, valve comm another p svalve which is in reverse 47 43 1 5 57 phase with respect to the firstoperating valve. A muffler which inhibits ice formation is operativeiyassociated with the damn CM operating valves for mufl'ling the noise ofthe air being ex- [56] I hausted from the air cylinder through theoperating valves UNITED STATES PATENTS with minimal accumulation of ice.

3,318.412 5/1967 Bailey ..18l/65 4Chl||1s,6l)rawin l"1gures 1 k a /B AIRSUPPLY PKTENTEDJUL 1 1 I972 SHEET 10F 4 AIR SUPPLY FIG. I

INVENTORS SAMUEL R. ROSEN ALVIN A. ROOD 8| DONALD R. SCHARF ATTORNEYSPATENTEDJUL 1 1 1972 3. 675 732 sum 3 c; 4

FIG. 3

INVENTORS- 2| SAMUEL R. ROSEN,

ALVIN A. ROOD a BY DONALD R. SCHARF M #Mmc/ 91 W ATTORNEYS PATENTEDJUL11 m2 SHEET l EF 4 5/ mvaw'ro SAMUEL R. ROSEN ALVIN A. R000 a BY DONALDRscH RF KM, I a awn ATTORNEYS MUFFLER Fox PNEUMATIC MOTOR CROSSREFERENCE TO RELATED APPLICATION This application is a division ofapplicants copending application, Ser. No. 809,235 filed Mar. 2 l 1969.

BACKGROUND OF THE INVENTION This invention relates to pneumatic motorsand especially to systems for controlling air motors with reciprocatingpistons used to drive associated equipment such as a pump piston. Aparticular aspect of the invention relates to a mulfling device formuffling noise generated by the exhaust of fluid from such pneumaticmotors.

The invention has particular utility in connection with single piston,double acting air motors used with double acting liquid pumps used topump liquid paint to a spray gun.

A particular problem in the art to which our invention pertains is thatof admitting air to and exhausting air from a pneumatic motor,particularly a double acting motor, with a minimum resistance to flow ofair to and from the cylinder of the motor. A particular problem whichhas been solved by our invention is the inhibition of the formation ofice in and around the locations where air is exhausted from thecylinders and where the presence of water vapor in the air and abruptdrop in pressure at the exhaust ports encourages the formation of ice.

While the invention will be described in connection with air motors andparticularly the problems deriving from the employment of moisture ladenair, air is illustrative of all compressible fluids which may beemployed in fluid motors controlled by our system advantageously.

As indicated above, the invention has particular utility in connectionwith die control of air motors for operating pumps for pumping paint orhot paint in the so-called hot airless method of spray painting. Thismethod is disclosed and discussed in detail in US. Pat. Nos. 2,754,228and 2,763,575 of James A. Bede. In this method the paint, whether hot orcold is projected from a small orifice nozzle under high pressure andthe continuity of an even pressure is most desirable to obtain the bestresults.

Such air motors have in the past conventionally been operated by meansof a four-way air valve such as that disclosed in US. Pat. No.3,176,719. The four-way air valve d'mclosed therein provides an exhaustpassage which is free from obstructions and which permits exhaust air toescape with a reduced tendency to form ice.

One problem associated with the prior art air motor control systemsutilizing the four-way air valve is that of excessive noise generated bythe exhaust of air. Also while the four-way air valve is effective toprevent formation of ice under most conditions, instances have occurredwhere under prolonged high speed operation ice does accumulate andadversely efiect the operation of the air motor, particularly when theexhaust air is passed through a mufller, ice then tending to form in themuffler.

The device of the present invention reduces the difliculties indicatedabove and affords other features and advantages heretofore notobtainable.

SUMMARY OF THE INVENTION It is among the objects of the invention tomuflJe the noise deriving from the exhaust of air from a double actingair motor.

Another object is to prevent the formation of ice in a manner harmful tonormal operation, during exhaust of air from a double acting air motor.

A further object is to provide a muffling device for a pneumatic motorthat will accomplish the foregoing objects and that is simple and ruggedin construction and economical to make and maintain.

These and other objects and advantages are accomplished in a singlecylinder double acting air motor that includes two operating valves fortransmitting fluid alternately to opposite ends of the cylinder to drivea piston, and for exhausting fluid alternately in opposite phase fromopposite ends of the cylinder. The operating valves are provided with amufller for receiving fluid exhausted from the cylinder through theoperating valves. The mufller comprises an open sided muffler boxdefining a chamber communicating with the exhaust ports of the operatingvalves. The open side is covered by a flat flexible closure platesecured to the body portion with marginal portions thereof spacedslightly outward from top edges of the side walls of the box to definenarrow spaces. When fluid is exhausted through the muffler, the platemay flex outwardly from the box due to fluid pressure so that any icewhich may tend to accumulate in the narrow spaces will increase the pressure and be blown out with additional flexing of the plate.

According to another aspect of the invention the muffler is thermallyinsulated from die operating valves by a thermal barrier means so thatthe valves will not lose heat to the muffler which is chilled due to theexpansion of air as it exits the exhaust ports. With this arrangementthe possibility that the valves may be chilled suificiently to cause iceto form therein from moisture laden air is substantially reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation of adouble acting liquid pump and associated single cylinder, double actingair motor including the muflling device of the invention;

FIG. 2 is a side elevation of the pump and air motor of FIG. 1;

FIG. 3 is a cross-sectional view of the air motor of FIGS. 1 and 2,drawn to an enlarged scale and taken on the line 2-3 of FIG. 1;

FIG. 4 is a sectional view taken on the line 4-4 ofFlG. 3;

FIG. 5 is a conal view taken on the line 5-5 of FIG. 3;

FIG. 6 is a fragmentary cross-sectional view taken on the line 6-6 ofFIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring more particularly tothe drawings and initially to FIGS. 1 and 2 there is shown a paintspraying apparatus for use in spraying liquid paint according to theso-called airless method described above in the Background of thelnvention. The apparatus comprises a double acting hydraulic pump A,driven by a double acting air motor B, and adapted to pump paint from apaint pail C to a spray gun D.

Paint from the paint pail C which may be, for example, a standard sizedrum, enters the hydraulic pump A through an inlet fitting 10 located atthe bottom thereof and exits through an outlet fitting I]. From theoutlet fitting 11 the paint is directed to another fitting 12 on a paintfilter 13 mounted on the pump A. The paint filter 13 serves to filterout solid particles within the paint that may be too large to passthrough the nozzle of the spray gun D.

The paint from the filter l3 exits through an outlet fitting 14 to aflexible hose 15 which extends to the spray gun I). The hose I5 '5preferably 25 feet or longer in order to provide some dampening effectin case of variable pressure output from the double acting pump A. Thehose 15 being resilient and flexible, absorbs some energy at the peakpressure periods and thus gives a smoother more uniform pressure outputto the spray gun D. The hydraulic pump A cycles at a rate typicallyabout 40 cycles per minute and in a typical instance would have about a4 cubic inch displacement.

Located at the upper end of the pump A is a solvent chamber 16 and anassociated filler cup 17. The chamber 16 maintains a bath of paintsolvent around the upper end of the pump piston 18 to dimolve any paintwhich may accumulate thereon and which when dry could seriously damagethe packing through which the upper end of the pump piston 18 slidesduring its pumping travel.

Air pressure for operating the air motor B is supplied by an air pump 20through a pressure line 21 which is connected to a AIR MOTOR ANDOPERATING VALVES The double acting air motor B best shown in FIG. 3comprises an air cylinder 30 mounted between an upper cylinder head 31and a lower cylinder head 32. The heads 31 and 32 are preferably formedof cast aluminum while the air cylinder 30 is of aluminum tube stockwhich has its interior surface hard anodized to accommodate frictionalloads and to minimize wear. Within the cylinder 30 is a piston 33mounted on a tubular piston rod 34.

Operating air enters the cylinder chamber and is exhausted therefrom inopposite phase through inlet-exhaust passages 35 and 36 located in theupper cylinder head 31 and lower cylinder head 32 respectively. Thecontrol of the inlet and exhaust of air from the respective ends of thecylinder chamber is accomplished by upper and lower poppet typeoperating valves 37 and 38 respectively (FIG. 3).

The valves 37 and 38 are located in an operating valve housing or block40 bolted at one end of the upper cylinder head 31 and at the other endof the lower cylinder head 32. The block 40 has a central air supplypassage 41 extending therethrough, which receives operating air from thepremure regulator valve 22 through an inlet fitting 42.

The valves 37 and 38 are poppet type valves essentially identical to oneanother and will be described and illustrated using the same numeralsfor corresponding parts. Each of the valves 37 and 38 is pilot operated,and has a control head 43 and an operating head 44 interconnected by abolt 45 which serves as a valve stem. The heads 43 and 44 are spacedfrom one another on the bolt 45 by a perforated spacer sleeve 46 whichis radially spaced from the bolt 45 and which extends transverselythrough the operating air pressure supply passage 41 with operating airbeing passed around the sleeve 46 or through the perforations in thesleeve 46.

The control head 43 moves or travels between limit positions within acontrol head chamber 47 defined by a recess in the valve block 40 and bya mating recess in an end block 48 bolted to the valve block 40 with asealing gasket interposed therebetween.

The operating head 44 travels axially between irdet and exhaustpositions in an operating head chamber 49 defined by a recess in thevalve block 40 and by a cover plate 50 which has exhaust ports throughwhich air may be exhausted from the cylinder through the valves 37 and38 to the muffler 23 when the respective valve 37 or 38 is in itsexhaust position (See valve 38 in FIG. 3).

The valves control the inlet and exhaust of air to the cylinders throughinlet exhaust passages 52 and 53 respectively formed in the valve block40 and which communicate between the operating head chambers 49 and theinlet-exhaust passages 35 and 36 respectively in the upper cylinder head31 and lower cylinder head 32.

The position of the operating valve 37 is controlled by a pilot valve 54which transmits a pressure signal to the chamber 47 of the respectivecontrol head 43 through a pilot air passage 55 in the valve block 40 anda mating pilot valve passage 56 in the upper cylinder head 3!. In likemanner the position of the operating valve 38 is controlled by a pilotrelay valve 57 which transmits a pressure signal to the chamber 47 ofthe respective control head 43 through a pilot relay air passage 58 inthe valve block 40 and a mating pilot relay air passage 59 in the uppercylinder head 31.

While the pressures used to transmit pressure signals to the operatingvalves 37 and 38, and the pressure in the operating air supply passage41 for operating the piston 33 are essentially the same, the operatingforce derives from the area differential between the outward face of thecontrol head 43 and its inward face. The eflective area against whichair pressure acts on the inner face is reduced by the valve stem so thatequal fluid pressures on opposite sides of the control head will inghead 44 will be moved to a position sealing the respective exhaust port31 while permitting operating air pressure to be transmitted through theperforations in the spacer sleeve 46, into the operating head chamber 49and out through the respective inlet-exhaust passage 52 or 53 in thevalve block 40 43 and operating head 44 to the right as viewed in FIG. 3where the operating head 44 will seal the chamber 49 from the main airsupply passage 41 while at the same time opening the respective exhaustport 51 so that air may be exhausted to the muffler 23 from theinlet-exhaust passage 52 or 53 respectively through the operating headchamber 49.

Accordingly, the operating heads 44 seat in two sealing positions, oneof which is against the cover plate 50 for the valve block 40 to sealthe exhaust port 5] and the other of which is against the inner wall ofthe chamber 49 formed by the valve block 40 to seal the chamber from themain air supply passage 41.

The pilot valve and pilot relay valve pressure signals are transmittedin opposite phase to the valves 37 and 38 respectively so thatcorrespondingly the positions of the operating heads 44 will be inreverse phase with one another and accordingly operating pressure willbe supplied to one end of the cylinder chamber while being exhaustedfrom the other end and vice versa during the operation of the air motor8.

According to a particular aspect of the invention a unique muffler 23 isprovided for reducing the noise caused by the rapid exhaust ofpressurized air from the cylinder chamber through the operating valves37 and 38. The unique construction of the mufller 23 minimizes theproblem of ice formation which is often encountered due to the rapidexpansion of moisture laden air as it a exhausted.

The mufl'ler 23 comprises a mufller box bolted to the operating valveblock 40. The box 110 has a floor with exhaust ports 11! formed thereinthat register with the exhaust ports 51 in the cover plate 50, and anopen top face which is covered by a cover plate 112 to define within thebox a muffler chamber 113. The cover plate 112 is formed of relativelythin flexible material and may have longitudinal reinforcing ribs 114.This construction permits the plate 112 to flex or bend resiliently in alaterial plane.

The cover plate 112 is secured to the box 110 in a manner to permit suchresilient flexing by means of three spaced bolts 1 15 which extendthrough the cover at spaced locations along a central longitudinal lineand which are received in posts 116 extending upwardly from the floor ofthe mufiler box 110. With this arrangement the plate 112 may flex orbend outwardly slightly in response to pressure within the mutflerchamber 1 13.

The sides of the top plate 112 are spaced from the adjacent edges of theside walls of the mulfler box I10 to define narrow exhaust spaces 117,approximately 0.015 inch wide through which exhaust air may escape fromthe muffler chamber 113. While ice may form in the narrow spaces "7 dueto the high velocity and rapid expansion of moisture laden air escapingtherethrough, such formation will increase the pressure within thechamber which in turn will cause the plate 112 to flex outwardly. Thisflexing will cause blow-out or purging of the ice from the spaces andthus prevent ice accumulation.

The muffler box 110 a thermally insulated from the valve block 40 by athermal barrier comprising both an insulating gasket 118 preferablyformed of a dielectric material. and an air space 119. Air is free tocirculate through the space 119 so that the operating parts of thevalves 37 and 38 will be maintained advantageously at a relatively warmtemperature and will not be chilled by the muffler box which is cooledby the rapid expansion of the air being exhausted therethrough.

While the invention has been shown and described with reference to aspecific embodiment thereof this is for the purpose of illustrationrather than limitation and other modifications and variations will beapparent to those skilled in the art upon reading of the specification,all with the intended spirit and scope of the invention. Accordingly thepatent is not to be limited to the form specifically illustrated anddescribed nor in any manner that is inconsistent with the extent towhich the progress in the art has been advanced by the invention.

What is claimed is:

l. A device for muflling the noise generated by gas being exhausted froma compressible fluid motor, comprising an open sided box defining achamber for receiving exhaust gases, a flexible closure plate adapted tocover the open side of said box with marginal portions thereof spacedslightly from the top edges of the side walls of said box to definenarrow exhaust spaces, said plate being mounted to permit flexingthereof to move said marginal portions outwardly from said box inresponse to pressure in said chamber.

2. The device of claim I including a thermal insulating means interposedbetween said device and said fluid motor to prevent chilling of adjacentparts of said fluid motor by conduction of heat to said mulfler box.

3. A device for muflling the noise generated by gas being exhausted froma compressible-fluid motor comprising a box defining a chamber forreceiving exhaust gases, said box having a pair of adjacent walls withtheir adjacent edges spaced slightly from each other to define a narrowexhaust space, at least one of said walls being flexible and beingmounted to permit flexing thereof to move its adjacent edge outwardlyfrom said box in response to pressure in said chamber to thereby widensaid exhaust space.

4. The device of claim 3 wherein said flexible wall is a flexibleclosure plate secured to said box at points defining a line about whichthe adjacent edge of said plate is flexed.

1. A device for muffling the noise generated by gas being exhausted froma compressible fluid motor, comprising an open sided box defining achamber for receiving exhaust gases, a flexible closure plate adapted tocover the open side of said box with marginal portions thereof spacedslightly from the top edges of the side walls of said box to definenarrow exhaust spaces, said plate being mounted to permit flexingthereof to move said marginal portions outwardly from said box inresponse to pressure in said chamber.
 2. The device of claim 1 includinga thermal insulating means interposed between said device and said fluidmotor to prevent chilling of adjacent parts of said fluid motor byconduction of heat to said muffler box.
 3. A device for muffling thenoise generated by gas being exhausted from a compressible-fluid motorcomprising a box defining a chamber for receiving exhaust gases, saidbox having a pair of adjacent walls with their adjacent edges spacedslightly from each other to define a narrow exhaust space, at least oneof said walls being flexible and being mounted to permit flexing thereofto move its adjacent edge outwardly from said box in response topressure in said chamber to thereby widen said exhaust space.
 4. Thedevice of claim 3 wherein said flexible wall is a flexible closure platesecured to said box at points defining a line about which the adjacentedge of said plate is flexed.